The purpose of this study was to investigate the effect of textual enhancement types on English as Foreign Language ( EFL ) learn er s ’ grammatical awareness of simple and complex structures. A nu m- ber of 104 learners from Ayandegan Institute, in Tehran, participated in this study. To homogenize the samples, the researchers administered a placement Michigan Test of English language to the pa r- ticipants . The participants were then divided into four groups, two experimental groups and t wo co n- trol groups. The two experimental groups went through enhanced forms of the texts containing si m- ple and complex structures, while the two control groups experienced unenhanced forms of the texts containing simple and complex structures. Before and af ter the treatment, a pretest and a posttest were run and the two reading texts with enhanced and unenhanced versions were used. The f indings showed that the textual enhancement had significant effect on learners’ grammatical awareness of simple and complex structures. There was also a significant difference between male and females’ scores in simple and complex structures.